A tunnel magnetoresistance element having an MgO tunnel barrier layer used as a sensor element of a magnetic random access memory (MRAM) or a magnetic head forms a structure in which a metal film (a magnetic film and a nonmagnetic film) and an insulator film are laminated in multiple layers. Such a magnetoresistance element is film-formed by a sputtering method excellent in productivity and then, by applying heat treatment while applying a high magnetic field at 1 tesla or more in another apparatus (heat treatment furnace in magnetic field) (See Non-Patent Document 1). As a method of forming an MgO tunnel barrier layer, a direct sputtering film-forming method by RF sputtering of an MgO target (See Patent Document 1), a method in which a metal Mg film is formed in an oxygen atmosphere by a reactive sputtering method after a metal Mg film is formed and then, oxidation treatment is applied at the last stage (See Patent Document 2), a method in which oxidation treatment is applied after a metal Mg film is formed and then, a metal Mg film is formed again at the last stage (See Patent Document 3), a method in which oxidation treatment is applied after a metal Mg film is formed and it is subjected to heat treatment and then, a metal Mg film is formed again and subjected to oxidation treatment (See Patent Document 4) and the like are disclosed.
As a method of forming an MgO tunnel barrier layer with a higher quality, as disclosed in Non-Patent Document 2, a method is known in which immediately after an MgO target is directly subjected to sputtering film formation by RF sputtering, a substrate is irradiated with infrared rays while the substrate is held in vacuum, and crystallization of an MgO film is promoted.
As a method of heating the substrate in vacuum at a high speed, in a step of forming a semiconductor element, as disclosed in Patent Document 5, a method is known in which a window which transmits heating light through a vacuum seal member such as an O-ring is provided in a vacuum chamber, and the substrate held in the vacuum chamber is heated by a radiation energy source which is arranged on the atmosphere side and radiates heating light such as an infrared lamp or the like.
Also, as a method of rapidly cooling a heated substrate, a method of cooling the substrate by moving it to a room adjacent to a heating chamber and thermally isolated therefrom is known as disclosed in Patent Document 6. In a cooling method of this method, it is devised that by directly placing the substrate on a cooled substrate supporting base, the substrate is rapidly cooled by heat transfer. As a method of cooling a substrate while the substrate is left in a heating chamber without being moved to a cooling chamber, as disclosed in Patent Document 7, a method is known in which a cooled gas is introduced into the heating chamber for cooling by using convection of a gas. In this method, an idea of improving cooling efficiency by inserting a shutter plate which shuts off residual heat from the radiation energy source between the radiation energy source and the substrate after the heating is finished is disclosed.
As a method of further improving cooling efficiency, as disclosed in Patent Document 8, a method of using a heat treatment device provided with a cooling source and a movable cooling plate fixed in the same space as the heating chamber is known. In the method disclosed in Patent Document 8, the movable cooling plate is arranged and cooled so as to be in contact with a cooling source while the substrate is heated. Then, after the heating of the substrate is finished, the movable cooling plate is separated from the cooling source and brought into contact with the substrate so that cooling is accomplished by heat transfer between the substrate and the movable cooling plate.
As another method of cooling the substrate in the same space as the heating chamber, Patent Document 9 discloses a method of indirectly cooling the substrate by bringing the movable cooling source into contact with the substrate supporting base incorporating a heating resistor body. Also, similar methods in which the substrate is heated or cooled by bringing the substrate supporting base into contact with a heat source or the cooling source are disclosed in Patent Documents 10 and 11.
In Patent Document 11, the substrate supporting base itself has heating and cooling functions and an electrostatic adsorption function for improving heating and cooling efficiency, and the substrate supporting base having the electrostatic adsorption function has a groove engraved on a face in contact with the back face of the substrate, and gas for promoting heat exchange is introduced into the groove.
As an example in which a heating source and a cooling source are provided separately in one vacuum chamber so as to directly heat and cool only the substrate, there is disclosed an example in Patent Document 12, in which a load lock chamber of a sputtering device is provided with a mechanism which heats with heating light from a lamp heater and a mechanism which brings the substrate into contact with the cooled substrate supporting base by electrostatic adsorption and cools it. In this example, since both mechanisms are provided in the load lock chamber, heating and cooling are not intended to be conducted continuously. However, by performing heating and cooling at evacuation and at ventilation of the load lock chamber, respectively, treatment time for sputtering film formation accompanying substrate heating is to be reduced.
An example in which a magnetic field is applied to the substrate arranged in the vacuum so as to process the substrate is disclosed in Patent Documents 13 to 15. The examples in Patent Documents 13 and 14 both relate to an apparatus which applies heat treatment to a plurality of substrates while applying the magnetic field in the vacuum, and it is devised that heat treatment can be performed in large quantity in a uniform magnetic field. However, they do not perform the film forming process and heating/cooling processing in a continuous vacuum. Also, the example in Patent Document 15 has an idea in which in an apparatus which performs sputtering film formation while applying a magnetic field to the substrate, a mechanism which rotates a magnet which generates a magnetic field parallel with the substrate face in synchronization with the rotation of the substrate is provided, so that the parallel magnetic field in one direction all the time with respect to the substrate can be applied.
Patent Documents 16 and 17 disclose a heat treatment apparatus provided with a heating mechanism which heats the substrate, a cooling mechanism which cools the substrate, and a moving mechanism which moves the substrate between a position close to or in contact with the heating mechanism and a position close to or in contact with the cooling mechanism in the same chamber.
In Patent Document 16, a substrate supporting body incorporating a heater is used as a heating mechanism and a cooling plate of a water-cooling type or a refrigerant cooling type is used as a cooling mechanism. If the substrate is to be heated by the heating mechanism, the substrate is heated by bringing the substrate into contact with the substrate supporting body heated by the heater. In another example relating to the substrate heating, the substrate and the substrate supporting body are separated in arrangement, and the substrate is heated by allowing heated dry gas such as nitrogen to flow between the substrate and the substrate supporting body. On the other hand, if the substrate is to be cooled, the cooling plate is cooled by a cooling fluid, and the substrate is cooled by bringing the substrate into contact with or close to the cooled cooling plate.
In Patent Document 17, a heating plate and a cooling plate are provided, and when the substrate is to be heated or cooled, the heating plate or the cooling plate is separated from the substrate by a predetermined interval.